• Economic and Environmental Geology
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• v.42 no.6
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• pp.561-574
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• 2009

Unsaturated/saturated groundwater flow and solute transport model, VSFRT2D(Variable Saturated Flow and Reactive Transport model) was developed considering effects of pumping, irrigation, and denitrification. VSFRT2D employed Richards equation as governing equation for groundwater flow and previously existing unsaturated models modified by including computational procedure of evapotranspiration at surface using Thornthwaite method when precipitation doesn't occur. Bioremediation processes based on monod kinetics are described using four nonlinear contaminant transport equations and three nonlinear microbes transport equations. The developed model was applied to field data in Hongsung area contaminated with nitrate. In order to identify the effect of precipitation, pumping, evapotranspiration, irrigation, fertilizer application, and various bioremediations on groundwater flow and contaminant transport, individual processes were separated and simulated. Then all results obtained from the individual processes are compared with each other. The simulation results show that bioremediation had a negligible effect on nitrate concentration change. However, pumping for irrigation, precipitation, and nitrogen fertilizer application showed profound influences on nitrate concentration change.

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.39-43
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• 2015

This study extends the Distributed Temperature Sensing (DTS) application to delineate the saturated zones in shallow sediment and evaluate the groundwater flow in both downward and upward directions. Dry, partially and fully saturated zones and water level in the subsurface can be recognized from this study. High resolution seepage velocity in vertical direction was estimated from the temperature data in the fully saturated zone. By a single profile, water level can be detected and seepage velocity in saturated zone can be estimated. Furthermore, thermal gradient analysis serves as a new technique to verify unsaturated and saturated zones in the subsurface. The vertical seepage velocity distribution in the recognized saturated zone is then analyzed with improvement of Bredehoeft and Papaopulos' model. This new approach provides promising potential in real-time monitoring of groundwater movement.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.370-376
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• 2011

To design the drainage system of a mine, it is very important to evaluate the groundwater inflow to the mine workings. In this study, continuous steady state flow through rock mass around mine openings developed in Sungok area of Gagok Mine was analyzed. Saturated only model and Saturated/unsaturated model were used as material models of rock mass. Groundwater quantities flowing into Sungok 160 level which is 1216 m long are computed as 1450 $m^3$/day in case of a saturated model and as 1071 $m^3$/day in case of a saturated/unsaturated model. An effect that hydraulic conductivity has on inflow turned out be greater than precipitation and inflow increased linearly with increase of hydraulic conductivity. It was found that change of hydraulic conductivity ratio and orientation have an impact on the variation of inflow and water table.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.87-99
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• 2016

We present the results of two-dimensional numerical simulations predicting the flow of groundwater in a fractured unsaturated zone. We applied the k-field distribution of permeability derived from discrete fracture network (DFN) modeling as the hydraulic properties of a model domain. To model an unsaturated zone, we set the depth from the ground surface to the underground aquifer. The rate of water infiltration into the unsaturated zone was divided into two parts, an artificial structure surface and unsaturated soil zone. The movement of groundwater through the unsaturated zone was simulated with particular emphasis on contaminant transport. It was clearly observed that the contaminants dissolved in groundwater transported vertically from the ground surface to the saturated zone.

• Geotechnical Engineering
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• v.8 no.1
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• pp.81-102
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• 1992

Landslides on hillside slopes with shallow soil cover over a sloping bedrock are frequently caused by increases in porewater pressures following of heavy rainfall and it is one of the most important factors of assessing the risk of landslide to predict the groundwater level fluctuations in hillslopes. This paper presents the comparative study of three unsaturated flow models developed by Sloan et al., Reddi, L.N., and Thomas, H.A., Jr., respectively, which are used to predict the increase of groundwater levels in hillside slopes. The parametric study for each of models is also presented. The Kinematic Storage Model(KSM) developed by Sloan et at. is utilized to predict the saturated groundwater flow. They are applied to the two sites in Korea so as to examine the possibility of use in the groundwater flow model. The results show that two unsaturated models developed by Sloan et al. and Reddi, L. N. are largely affected by the uncertain parameters like saturated permeability and saturated water content : the abed model has the potential of use in unsaturated flow model with the optimal estimates of model parameters utilizing available optimization techniques. And it is also found that the KSM must be modified to account for the time delay effect in the saturated zone. The results of this paper are able to be utilized in developing the predictive model of groan dwater level fluctuations in a hillslope.

• Geotechnical Engineering
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• v.9 no.2
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• pp.65-69
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• 1993

강우에 의해 발생되는 토양(soil)에서의 Recharge를 구하기 위해 두가지 모델 즉, ((i) Simple Mass Balance Model (ii) Numerical Model : UNSAT 1)을 사용했는데, 이 두 모델들은 불포화상태의 흙(unsaturated zone : above groundwater table)에서 그의 가정과 개념에 약간 차이가 있다. Unsaturated Zone에서의이 두 모델의 적용에 있어서 몇가지 중요한 사항이 지적되고 있는데, 균질의 불포화 영역(unsaturated zone)의 토양에서 Mass Balance Model을 사용함으로써 얻은 Recharge는 UNSAT 1(numerical model)을 통해 얻은 결과와 비교할 때 서로 상이한 결과를 보였다. 또한, Recharge의 계산에 있어서 지하수위의 변화에 따른 영향을 알아보기 위해 Sensitivity Analysis를 수행하였다. 즉, 고정수위(fixed groundwater table)로 가정했을 때 발생되는 오차를 한개의 수리학적 계수(hydraulic parameter)의 함수로 보고 계산을 했으며 이 결과를 그림으로 나타내어 보았다. 이 연구의 결과는 Model Simulation에 있어서 수리학적 경계조건을 결정하는데 큰 도움이 될 것이며, 또한 이 연구에서는 Unsaturated-Saturated Flow Model이나 Drainage Model을 함께 병행시켜 Simulation을 수행하는데 촛점을 두고 있다.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.75-89
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• 2013

This paper describes a GIS-based geohydrologic methodology, called YSGWF (YonSei GroundWater Flow) for predicting the rainfall infiltration-groundwater flow of slopes. This physical-based model was developed by the combination of modified Green-Ampt model that considers the unsaturated soil parameters and GIS-based raster model using Darcy's law that reflects the groundwater flow. In the model, raster data are used to simulate the three dimensional inclination of bedrock surface as actual topographic data, and the groundwater flow is governed by the slope. Also, soil profile is ideally subdivided into three zones, i.e., the wetting band zone, partially saturated zone, and fully saturated zone. In the wetting band and partially saturated zones the vertical infiltration of water (rainfall) from surface into ground is modeled. When the infiltrated water recharges into the fully saturated zone, the horizontal flow of groundwater is introduced. A comparison between the numerical calculation and real landslide data shows a reasonable agreement, which indicate that the model can be used to simulate real rainfall infiltration-groundwater flow.

• Water for future
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• v.22 no.3
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• pp.289-298
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• 1989

A review is made of transient phenomena ralation to flow in the vadose zone. Reviewed topics include rapid water table response to rainfall, pulsating flow due to pressure perturbations in the vasoes zone, and the wave-like propagation of increased soil moisture caused by intermittent rainfall. As a basis of interpreting these phenomena, zoning of the vadose zone into a residual water zone, an unsaturated capillaty zone, and a saturated capillary zone are proposed. Possible implications with respect to hydrological processes relating to these phenomena are discussed.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.1-15
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• 1999

An artificial recharge test was performed to analyze the source of seepage observed inside the Songsanri tombs Kongju during the rainy season. In order to simulate simulate the test, a two-dimensional unsaturated groundwater flow model was developed. By the measured water level variation in the observation wells and in the artificail water tank, the model was cailbrated to estimate the model parameters such as fitting parameters in the constitutive relations(n and $\alpha$), the saturated volumetric water content, the residual volumetric water content, and the saturated hydraulic conductivity. Using the calibrated parameters, the recharge test was simulated. The results of the test and simulation show that the major source of the seepage is the downward groundwater flow through cracks in the protection layer the tombs. It was also analyzed by the steady state simulation that, with a perfect protection layer, a long-term precipitation that, with a perfect protection layer, a long-term precitation could cause only 10% increase of the effective saturation around the north side of the Muryong royal tomb by infiltration of the unsaturated groundwater from the North. Therefore, it is concluded that the most urgent protection plan for the tombs with respect to seepage is to reconstruct an effective waterproof-layer rather than a trenched drainage system.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.431-434
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• 2003

This research developed a method for the estimation of groundwater recharge by yielding daily soil moisture content and watershed evapotranspiration from the water balance concept of the unsaturated and saturated layers in rainfall-runoff model called DAWAST. The goal of the research is to estimate the groundwater recharge fulfilling conditions of the safe discharge for any season. To meet this goal, the data of groundwater level and stream flow rate have been monitored in a study area and used to validate the model.